According to a vehicle approach warning system disclosed in JP 2008-197720A for example, a vehicle is equipped with a radar device for detecting an object body such as a person, an infrared camera for imaging the object body and a sound generator for generating warning sound based on data acquired by the radar and the infrared camera. Specifically, the sound generator recognizes a person based on the acquired data and generates warning sound only when the recognized person is moving in a direction, which crosses a direction of travel of the vehicle. It is thus possible to inhibit generation of the warning sound when the person is already aware of approach of a vehicle and limit generation of the warning sound to only cases that the person will have a risk of touching the vehicle.
According to the conventional technology, it is assumed that the person is not aware of approaching of the vehicle if the direction of movement of the person includes a direction component, which is perpendicular to the direction of travel of the vehicle.
A person normally keeps standing beside a traffic lane, on which a vehicle is traveling, before crossing a road. In this instance, the person may keep directing his/her face on a vehicle approaching on the opposite traffic lane and be unaware of a vehicle, which is approaching on the traffic lane closer to the person. Thus, in some instances, the person is not aware of approach of a vehicle even when the person is not moving. The vehicle should provide warning sound in such a case, because the person may start to move into the traffic lane to cross the road. Therefore, the conventional technology is not satisfactory in that the sound warning is limited to cases, in which the person is moving.